Lumbar puncture (LP) is an attractive route for delivering novel therapies to the nervous system because it is safe in patients;performed at the bedside;and FDA-approved for conventional drugs. However, its use for gene delivery has to date been ineffective;has not met safety principles;and has failed to target neurons. We have developed highly effective gene transfer to the primary sensory neurons of the dorsal root ganglia (DRGs) via LP, i.e. intrathecally (IT), using self-complementary recombinant adeno-associated virus serotype 8 (sc-rAAV8). A single administration of sc-rAAV8 expressing the analgesic gene prepro-[unreadable]-endorphin (pp[unreadable]EP) or a mutant form of the rat anti- inflammatory gene interleukin-10 (rIL10/F129S) led to highly significant (p<0.0001) relief of symptoms for =3 months in a rat chronic neuropathic pain model, an important functional outcome. The hypothesis of this application is that sc-rAAV8 via LP is a viable gene delivery product for intractable chronic pain usable by clinicians outside of specialized research centers. In order to investigate/establish the potential for clinical translation, we propose the following Specific Aims: Aim 1. To quantify DRG transduction by stereology in the "closed" vs. "open" IT space, characterize serological immunity to the IT vector, and determine organ distribution. Aim 2. To identify the strongest candidate therapeutic gene in the neuropathic pain model and to define if there is pharmacological synergy with conventional pain treatments. Aim 3. To test the antinociceptive efficacy of the approach in a new rat model reflecting pain in patients with incurable cancer, a possible future clinical trial-scenario. Aim 4. To test if IT sc-rAAV8 effectively transduces DRG neurons in large animals. Significance &future perspective: Chronic pain affects 50 million Americans and incurs costs of >$100 billion/year in the US alone (as stated in PA-07-282). This application proposes a gene therapy approach, which, if the Research Plan succeeds, will become a candidate for clinical development in patients with severe pain from advanced malignancies. IT sc-rAAV8 may serve as a tool for proof-of-mechanism trials, e.g. to validate microglial activation as therapeutic target in humans, and may also become a new drug for otherwise intractable chronic pain. Public Health Relevance: Chronic pain affects 50 million Americans and incurs costs of >$100 billion/year in the US alone (as stated in PA-07-282). Spinal tap is an attractive route for delivering novel therapies to the nervous system for a variety of diseases but particularly for pain. The reason is that the spinal cord functions as a "pain gate" able to open wide and thereby to facilitate pain signal transfer or to "close" and thereby control pain. A spinal tap is is safe in patients;performed at the bedside;and FDA-approved for conventional drugs. We have developed a gene therapy method administering new gene vectors by spinal tap, which control pain. Specifically, we find in a rat model that a severe type of pain, chronic neuropathic pain can be controlled for >3 months by our approach. In the research proposed in this application, we wish to study and improve our approach further in order to evaluate, whether it is a viable treatment approach for future development for human use with a special focus on severe pain from advanced cancer.